Education in Schools: How soon is your child learning sex ed?

Do any of you remember the day that you were taught about the human reproductive system? What grade were you in? Just recently, my 11 year old son and I were having our daily talk about what he was learning in school. He is in the fifth grade and I always love hearing his stories about what happend in school that day. What my son said next shocked me. I asked him what he was learning and he told me "We are learning about semen". Needless to say my jaw hit the floor and I was stunned. Either I am getting too old, or they have started teaching that fundamental a bit early. Since when, do 11 year old children need to know about semen? I know that this is an explict contented blog, but I wanted to get someone elses opinion about this. How soon is too soon?